Acquisition Portfolio Optimization

With a plethora of digital media channels at our disposal, and new ones on the way every day (!), how do you prioritize your efforts? How do you figure out which channels to invest in more and which to kill? How do you figure out if you are spending more money reaching the exact same current or prospective customers multiple times? How do you get over the frustration of having done attribution modeling and realizing that it is not even remotely the solution to your challenge of using multiple media